Osmoprotectants and Antioxidative Enzymes as Screening Tools for Salinity Tolerance in Radish (Raphanus sativus)

The research addresses the identification of a screening methodology for salt stress tolerance in radish cultivars. In the first experiment, two different radish cultivars (long white and round red) were compared in their morphological and physiological responses to different salinity levels. Round red radish showed better morphological and physiological responses to incremental salinity in terms of yield and better adaptation of overall water relations. In the second experiment, the most tolerant genotype from the first experiment was used as a control against other seven round red radish genotypes ranked by their salinity tolerance according to morphological, physiological and biochemical indices. Salt stress did not significantly affect malondialdehyde (MDA) and hydrogen peroxide (H2O2) content, and ascorbate peroxidase (APX) activity in the studied cultivars. Nonetheless, the relatively salt tolerant cultivar SAXA2 showed higher ability to accumulate compatible solutes (e.g. proline and proteins) and maintain osmotic adjustment. In addition, cultivar SAXA2 also showed considerable increase in glutathione reductase (GR) activity. Our results supported that accumulation of proline and higher GR activity are associated with radish salt tolerance, whereas no relationship with salinity was observed in superoxide dismutase (SOD), MDA and H2O2 content.